Patent Grant
9756696
Light emitting diode (LED) lighting systems are becoming more prevalent as replacements for existing lighting systems. LEDs are an example of solid state lighting and have advantages over traditional lighting solutions such as incandescent and fluorescent lighting because they use less energy, are more durable, operate longer, can be combined in multi-color arrays that can be controlled to deliver virtually any color light, and contain no lead or mercury. In many applications, one or more LED dies (or chips) are mounted within an LED package or on an LED module, which may make up part of a lighting system, a light fixture, lighting unit, lamp, “light bulb” or more simply a “bulb,” which includes one or more power supplies to power the LEDs. An LED fixture may be made in the form of a fixture to be used in place of or instead of a standard incandescent or fluorescent fixture.
Light of varied color hues, or differing correlated color temperature (CCT) can be created by combining LEDs with different emission color points or “color bins.” These bins can vary somewhat and be adapted by using firmware to set drive current and therefore brightness. Typically, the lighting system is designed so that each color light source can be managed separately based on the drive current characteristics for that color. The power supply or “driver” is designed to match the configuration of LEDs in the lighting system so that precise control can be accomplished by using separate color control channels. With such an arrangement, a desired CCT can be maintained at any dimming level or user-configurable CCT can be provided. As one example, an LED lamp can be dimmed following the logarithmic profile of color vs. brightness exhibited by incandescent lamps. For some LED lighting products, there is a need to use an independent or pre-existing constant-current driver for the LEDs. With such a driver, the color control described above cannot be accomplished by independently addressing the current supplied by the driver to each color of LED.
Embodiments of the invention provide a lighting apparatus for use with a constant-current driver in which current diverted from some LEDs to alter the color point of the LEDs is diverted through an shunt path that includes additional LEDs, so that the diverted power still produces light and is not wasted. A signal fed to this shunt path from a controller effectively controls the balance of drive current between two segments of LEDs.
In some embodiments, a lighting system includes a string of LEDs, wherein specific LEDs are operable to emit different colors of light. The string includes a plurality of series-connected color segments. A shunt segment includes additional LEDs. The LED shunt segment is connected in parallel with at least one of the color segments. A controller is connected to the LED shunt segment to selectively balance drive current between the LED shunt segment and the color segment to which it is connected in parallel so that a color temperature of light emitted from the lighting system is controllable by the controller.
In some embodiments, first, second, and third series-connected color segments of series-connected LEDs in a lighting system or solid-state light-emitting apparatus are connectable to a power supply. Each color segment of LEDs operable to emit light of a differing color. A passive shunt circuit is connected in parallel with the first color segment of LEDs and the LED shunt segment comprising LEDs operable to emit light of an additional color is connected in parallel with the second color segment of LEDs. The controller is connected to the passive shunt circuit and the LED shunt segment to independently and selectively divert drive current from the first and second color segments so that a color temperature of light emitted from the apparatus is controllable by the controller. In some embodiments, a plurality of strings of LED devices can be used, wherein at least string one includes multiple color segments.
In any of the embodiments described above, the controller can be responsive to the varying input current and/or voltage of the power supply for the system to alter the drive current through either or both the shunt segment and passive shunt circuit in response to dimming, for example, to achieve so-called “sunset” dimming where the CCT of the lighting system follows the logarithmic profile of color vs. brightness exhibited by incandescent lamps. In some embodiments, the LEDs in the LED shunt segment emit substantially red light. In any of the embodiments, the controller can be responsive instead, or in addition, to user input, which may be provided through an interface specifically used to adjust color temperature.
In any of the embodiments, the color temperature of the system or apparatus can be between 1200K and 3500K. In any embodiment, the color temperature of the system or apparatus can be between 1800K and 3500K. In any embodiment, the color temperature can be reduced from about 3000K to about 2200K during dimming. In some embodiments, the controller is connected to a color segment and a shunt circuit or shunt segment through a transistor, and the controller is operable to control current shunting by applying a pulse-width modulation (PWM) signal to the transistor. The power supply or driver can be included as part of the system or can be connected externally.
In any of the embodiments described above, the first color segment of the lighting system or apparatus can emit substantially red light and the second color segment can emit substantially low blue-shifted yellow (BSY) light. The third color segment can emit light, which can include high BSY light and/or substantially red light. The additional color of the LEDs in the LED shunt segment can be the same or nearly the same as one of the colors used in the color segments, or be different. In any of the embodiments, the LED shunt segment can emit substantially red light or red-orange light.
Embodiments of the invention operate under control of a programmed processor, such as a microprocessor, microcontroller, ASIC, or even a “processor” comprising dedicated circuits, with or without firmware. The color temperature to be emitted by the LED lighting system is determined based on user input, varying input current and/or voltage suggestive of dimming or brightening, or both. The drive current for the string of LEDs configured in one of the ways described above is measured. The processor determines output values for at least some of the plurality of color segments to achieve the color temperature, and outputs a signal to divert drive current from a color segment at least to an LED shunt segment connected in parallel with one of the color segments. This process repeats whenever there is a change in the color temperature needed. In some embodiments the signal is a PWM signal and in some embodiments, current is redirected from one of the color segments to a passive shunt circuit as well as an LED shunt.
The appropriate values for the LEDs in a color segment in any of the above-discussed embodiments can be calculated by evaluating a polynomial equation. Alternatively, these values can be calculated by accessing a look-up table. In any of these embodiments, the processor can constrain output values based on a stored minimum and maximum value. In any of the above-mentioned embodiments, the temperature of the LEDs or elsewhere within a lighting system can be monitored and used in calculating the appropriate output values.
Embodiments of the present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that when an element such as a layer, region or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.
Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer or region to another element, layer or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Unless otherwise expressly stated, comparative, quantitative terms such as “less” and “greater”, are intended to encompass the concept of equality. As an example, “less” can mean not only “less” in the strictest mathematical sense, but also, “less than or equal to.”
The terms “LED” and “LED device” as used herein may refer to any solid-state light emitter. The terms “solid-state light emitter” or “solid-state emitter” may include a light emitting diode, laser diode, organic light emitting diode, and/or other semiconductor device which includes one or more semiconductor layers, which may include silicon, silicon carbide, gallium nitride and/or other semiconductor materials, a substrate which may include sapphire, silicon, silicon carbide and/or other microelectronic substrates, and one or more contact layers which may include metal and/or other conductive materials. A solid-state lighting device produces light (ultraviolet, visible, or infrared) by exciting electrons across the band gap between a conduction band and a valence band of a semiconductor active (light-emitting) layer, with the electron transition generating light at a wavelength that depends on the band gap. Thus, the color (wavelength) of the light emitted by a solid-state emitter depends on the materials of the active layers thereof. In various embodiments, solid-state light emitters may have peak wavelengths in the visible range and/or be used in combination with lumiphoric materials having peak wavelengths in the visible range. Multiple solid-state light emitters and/or multiple lumiphoric materials (i.e., in combination with at least one solid-state light emitter) may be used in a single device, such as to produce light perceived as white or near-white in character. If multiple emitters are used in a device, the device may still be referred to as an “LED” or “LED device.” In certain embodiments, the aggregated output of multiple solid-state light emitters and/or lumiphoric materials may generate warm white light output having a color temperature range of from about 2700K to about 4000K.
Solid-state light emitters may be used individually or in combination with one or more lumiphoric materials (e.g., phosphors, scintillators, lumiphoric inks) and/or optical elements to generate light at a peak wavelength, or of at least one desired perceived color (including combinations of colors that may be perceived as white). Inclusion of lumiphoric (also called ‘luminescent’) materials in lighting devices as described herein may be accomplished by direct coating on solid-state light emitter, adding such materials to encapsulants, adding such materials to lenses, by embedding or dispersing such materials within lumiphor support elements, and/or coating such materials on lumiphor support elements. Other materials, such as light scattering elements (e.g., particles) and/or index matching materials may be associated with a lumiphor, a lumiphor binding medium, or a lumiphor support element that may be spatially segregated from a solid-state emitter.
As used herein, the term LED may comprise packaged LED chip(s) or unpackaged LED chip(s). LED elements or modules of the same or different types and/or configurations. The LEDs can comprise single or multiple phosphor-converted white and/or color LEDs, and/or bare LED chip(s) mounted separately or together on a single substrate or package that comprises, for example, at least one phosphor-coated LED chip either alone or in combination with at least one color LED chip, such as a green LED, a yellow LED, a red LED, etc. The LED module can comprise phosphor-converted white or color LED chips and/or bare LED chips of the same or different colors mounted directly on a printed circuit board (e.g., chip on board) and/or packaged phosphor-converted white or color LEDs mounted on the printed circuit board, such as a metal core printed circuit board or FR4 board. In some embodiments, the LEDs can be mounted directly to the heat sink or another type of board or substrate. Depending on the embodiment, the lighting device can employ LED arrangements or lighting arrangements using remote phosphor technology as would be understood by one of ordinary skill in the art, and examples of remote phosphor technology are described in U.S. Pat. No. 7,614,759, assigned to the assignee of the present invention and hereby incorporated by reference.
In those cases where a soft white illumination with improved color rendering is to be produced, each LED element or module or a plurality of such elements or modules may include one or more blue shifted yellow LEDs and one or more red or red/orange LEDs as described in U.S. Pat. No. 7,213,940, assigned to the assignee of the present invention and hereby incorporated by reference. In some embodiments, each LED element or module or a plurality of such elements or modules may include one or more blue LEDs with a yellow or green phosphor and one or more blue LEDs with a red phosphor. The LEDs may be disposed in different configurations and/or layouts as desired, for example utilizing single or multiple strings of LEDs where each string of LEDs comprise LED chips in series and/or parallel. Different color temperatures and appearances could be produced using other LED combinations of single and/or multiple LED chips packaged into discrete packages and/or directly mounted to a printed circuit board as a chip-on board arrangement. In one embodiment, the light source comprises any LED, for example, an XP-Q LED incorporating TrueWhite® LED technology or as disclosed in U.S. Patent Application Publication 2013/0328073, entitled “LED Package with Multiple Element Light Source and Encapsulant Having Planar Surfaces” by Lowes et al., published Dec. 12, 2013, the disclosure of which is hereby incorporated by reference herein, as developed and manufactured by Cree, Inc., the assignee of the present application. If desirable, other LED arrangements are possible. In some embodiments, a string, a group of LEDs or individual LEDs can comprise different lighting characteristics and by independently controlling a string, a group of LEDs or individual LEDs, characteristics of the overall light out output of the device can be controlled.
It should also be noted that the term “lamp” is meant to encompass not only a solid-state replacement for a traditional incandescent bulb as illustrated herein, but also replacements for fluorescent bulbs, replacements for complete fixtures, and any type of light fixture that may be custom designed as a solid state fixture. The term “LED lighting system” or the term “solid-state lighting system” as used herein can refer to a fixture, an assembly, a light engine, a lamp, a bulb, or any other solid-state lighting arrangement. Mounting arrangement could include a mounting plate with appropriate tabs, holes, or the like to engage with a portion of a pre-existing light fixture.
In example embodiments, three LED color points are mixed to produce white light in an LED arrangement, apparatus, or system. These bins can vary somewhat and be adapted by firmware. Depending on the embodiment, different numbers of color points are possible. The light source is driven by an external constant-current driver, which sets the drive current and therefore overall brightness. The light source is managed by an on-board microprocessor that senses operating conditions and outputs two pulse-width modulation (PWM) signals to control current flow in the LEDs. The light source senses the drive current and can use this information to change correlated color temperature (CCT) according to a dimming profile to accomplish sunset dimming. Alternatively, the CCT can be changed at the command of a user through a user interface to achieve various effects. In such a case, the lighting apparatus receives a separate input of information that indicates what the desired color temperature is and the lighting apparatus can maintain that color temperature at any dimming level.
The same LED arrangement can accomplish any subset, variant, or combination of these color control options—examples include: operating on a reduced range of sunset dimming (e.g. 3000K-2200K); using a combination of color-changing and non-color-changing over dimming (e.g. hold CCT until 50% brightness and then shift warmer below there); dim following the logarithmic profile of color vs. brightness exhibited by incandescent lamps. The control information that instructs the apparatus on what function to perform can be achieved through a variety of methods and/or different types of user interfaces—for example: configuration by jumpers, switches, or an electronic tool on the fixture manufacturer's production line; a 0-10V, DALI, DMX, or other lighting control signal into the light source; a standard or known lighting control signal connected into a constant-current driver, which is then passed on to the lighting apparatus by some other means (I2C, UART, SPI, analog voltage, etc.); a control input by the user that is transmitted to the light source by RF, infrared, etc.
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In the above-discussed embodiment, the primary task of firmware on the microcontroller is to measure conditions and use the current and temperature information to produce a corresponding PWM output signal. The transfer function between the inputs and outputs is usually referred to as a curve, and may be implemented as a lookup table in the firmware, or as a polynomial equation or equations, depending on the complexity of the curve shape and the memory and speed constraints on the microcontroller. It is also possible to implement this control with discrete circuitry instead of a programmed microprocessor. Depending on the embodiment, other control circuitry can be used using a software-driven controller, firmware, hardware, discrete analog and/or digital devices or any combination thereof. Such circuitry for purposes of this disclosure can also be referred to as a controller.
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output=44.41i−0.731
output=446.428751i2+69.642857i+147.5
As should be apparent to those who program microprocessors, calculating values using the above equations directly requires floating point mathematics, which is computationally expensive. The output can be instead calculated using bitwise shifts, as shown below.
output=44.41i−0.731
output=446.428751i2+69.642857i+147.5
output=1421*i>>5−1
output=3571*i2>>3+557*i>>3+148
As an alternative to implementing equations like those shown above, a look-up table can be stored in the processor to enable determination and/or calculation of output values for the LEDs. The table below can be used for the red LEDs in lieu of the equations shown.
In some embodiments, a general-purpose processor such as a digital signal processor, microcontroller, or microprocessor (μP) is used and non-transitory firmware, software, or microcode can be stored in a tangible storage medium that is within or associated with the system or apparatus. Such a medium may be a memory integrated into the processor, or may be a memory chip that is addressed by the processor to perform control functions. Such firmware, software or microcode is executable by the processor and when executed, causes the microcontroller unit to perform its control functions. Such firmware or software could also be stored in or on a tangible medium such as an optical disk or traditional removable or fixed magnetic medium such as a disk drive used to load the firmware or software into a an apparatus or system for maintenance, update, manufacturing, or other purposes. The firmware causes the processor to control an LED lighting apparatus or system to operate according to one of the embodiments described.
Any of the embodiments disclosed herein may include power or driver circuitry having a buck regulator, a boost regulator, a buck-boost regulator, a fly-back converter, a SEPIC power supply or the like and/or multiple stage power converter employing the like, and may comprise a driver circuit as disclosed in U.S. patent application publication 2015/0312983, entitled “High Efficiency Driver Circuit with Fast Response” by Hu et al., published Oct. 29, 2015, or U.S. Pat. No. 9,303,823, issued Apr. 5, 2016, entitled “SEPIC Driver Circuit with Low Input Current Ripple” by Hu et al. incorporated by reference herein. The circuit may further be used with light control circuitry that controls color temperature of any of the embodiments disclosed herein, such as disclosed in U.S. patent application publication 2015/0351187, entitled “Lighting Fixture Providing Variable CCT” by Pope et al., published Dec. 3, 2015, incorporated by reference herein. Additionally, any of the embodiments described herein can include driver circuitry disclosed in U.S. patent application Ser. No. 15/018,375, titled “Solid State Light Fixtures Having Ultra-Low Dimming Capabilities and Related Driver Circuits and Methods,” filed Feb. 8, 2016 and assigned to the same assignee as the present application, the entirety of this application being incorporated herein by reference.
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Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown and that the invention has other applications in other environments. This application is intended to cover any adaptations or variations of the present invention. For example, embodiments are described as having a single string with multiple color segments. A single string or segment can include LEDs, strings or segments of LEDs that are in a serial/parallel arrangement. Additionally, embodiments of the present invention can use multiple strings where at least one string comprises a single string with multiple color segments and the other strings have the same or different structures. In some embodiments, there can be multiple strings wherein each string comprises multiple color segments. Additionally and depending on the embodiments, the LEDs can be the same strings. Alternatively, additional strings can be used in parallel. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 7213940 | Van De Ven et al. | May 2007 | B1 |
| 7614759 | Negley | Nov 2009 | B2 |
| 8598809 | Negley et al. | Dec 2013 | B2 |
| 8698388 | Cash | Apr 2014 | B2 |
| 8729589 | Hussell | May 2014 | B2 |
| 8950892 | Cash | Feb 2015 | B2 |
| 9052067 | van de Ven et al. | Jun 2015 | B2 |
| 9131571 | Zhang et al. | Sep 2015 | B2 |
| 9303823 | Hu et al. | Apr 2016 | B2 |
| 20110068702 | van de Ven | Mar 2011 | A1 |
| 20120306375 | van de Ven | Dec 2012 | A1 |
| 20130328073 | Lowes et al. | Dec 2013 | A1 |
| 20140197750 | Cash | Jul 2014 | A1 |
| 20140210364 | Cash et al. | Jul 2014 | A1 |
| 20140252967 | van de Ven et al. | Sep 2014 | A1 |
| 20150189708 | Cash | Jul 2015 | A1 |
| 20150312983 | Hu et al. | Oct 2015 | A1 |
| 20150330581 | van de Ven et al. | Nov 2015 | A1 |
| 20150351187 | McBryde et al. | Dec 2015 | A1 |
| Entry |
|---|
| U.S. Appl. No. 15/018,375, filed Feb. 8, 2016. |
